An important object of this invention is to eliminate as much of the waste yarn created as a result of trimming the carpet to its finished width, usually 144" or 162" or 180", after a final manufacturing step such as lamination of the secondary backing or application of foam padding. Currently a manufacturer of tufted carpets and the like cannot rely on a consistent width of primary backing, usually woven polypropylene. For example, backing fabric received from suppliers for 144" carpet may be provided in a minimum width of 150". This minimum width is often controlled quite well but a very high proportion of backing may often vary to as much as 156" wide. This means that feelers and others with sensors such as those illustrated in U.S. Pat. No. 3,779,186 are relatively ineffective in properly presenting the backing to the needles of the tufting machine.
On each selvage there is a reinforcement for pinning of between 3/4" and 1" wide. The weakness and porosity of this backing precludes the successful tenter frame dryer pinning anywhere other than in the reinforcement. Also, there is a variance in the backing width of an individual roll that is run on a give tufting machine. There is a width variation when the same style is run on another tufting machine, along with the lack of centering the tufting needles on the backing on any tufting machine that can make it virtually impossible for any operator to run a production lot from one or several tufting sources at the same density or frame width. This problem resulted in the necessity to tuft at least 11/2" additional width, which is subsequently cut off prior to shipment in order to insure that a full width carpet will result.
Efforts to deal with the problem varying backing widths and lateral movements thereof with respect to the needles have included the provision of longitudinal chains with attached gripping means for engaging the side edge portions of the backing material for positively positioning the backing in proper lateral position as disclosed in U.S. Pat. No. 3,865,059. A later attempt to solve the problem has included the making of the waste or salvage portion which is trimmed away from low cost waste yarn rather than from first quality yarn used to produce the main or central portion of the carpet as described in U.S. Pat. No. 4,077,434. The use of a folded selvage for another purpose is illustrated in U.S. Pat. No. 3,848,435.